Problem: Which of these numbers is composite? ${7,\ 16,\ 61,\ 71,\ 89}$
A composite number is a number that has more than two factors (including 1 and itself). 7, 61, 71, and 89 each have only two factors. The factors of 16 are 1, 2, 4, 8, and 16. Thus, 16 is the composite number.